In order to enhance the strength of concrete used for pipe, drainage structures, building structures, bridge beams, concrete highways and so forth, the concrete is typically reinforced with a latticework of rebar or wire mesh steel in single or multiple layers. The rebar or wire is typically laid out in a grid-like pattern or framework in a concrete form and secured together loosely using wire ties. The ties hold the reinforcement steel in place while the concrete is being poured around it. After the concrete sets, the reinforcement steel members become permanently positioned within the concrete.
Most reinforcement steel members used in commercial concrete construction have been tied together in the same way for many years. The wire ties, typically comprising very light gage, mild steel wire supplied on a belt-mounted reel, are pulled off the belt-mounted reel, wrapped around the reinforcement steel members, pulled taut with conventional side cutters or pliers, twisted, and cut. This conventional method of tying together reinforcement members is very labor intensive and adds considerable costs to concrete construction jobs. Further, the difficulty associated with the conventional method has often resulted in the reinforcement members being tied defectively, resulting in weak points within the structure.
Several clips have been developed for use in concrete construction to overcome the disadvantages of conventional manually applied ties. For example, U.S. Pat. No. 3,331,179 discloses manufactured spacer rings intended to ease the process of securing reinforcement steel members together during concrete construction. The manufactured spacer rings secure a grid of reinforcement steel members at the intersection points of the reinforcement steel rods. The manufactured spacer rings are formed with a split for spreading the rings to facilitate mounting over the reinforcement steel rods. After the ring is mounted, release of the spread ring results in the ring closing upon the rods due to the elasticity of the material.
While effective, the manufactured spacer rings disclosed in U.S. Pat. No. 3,331,179 are expensive to manufacture. The spacer rings require a relatively large amount of spring steel material to perform the intended function of spacing the grid away from the bottom surface of the concrete form and yet provide the elasticity to reclose the ring upon the rods after the ring is spread to mount the ring over the rods. Moreover, such manufactured spacer rings are inefficient to use because they require a rather difficult and tedious process of spreading the rings during installation.
U.S. Pat. Nos. 5,881,452 and 5,938,099 each disclose an apparatus for tying fasteners suitable for use in concrete construction. The '452 patent discloses a hand held apparatus that is powered by pneumatic pressure supplied by a compressed air force. Similarly, the '099 patent discloses a hand held machine that uses power from outside sources instead of manual power. Thus, each device has the inherent disadvantages of increased cost and limited mobility associated with externally powered devices.
Similar tying devices have been utilized in conjunction with hog rings. For example, U.S. Pat. Nos. 3,628,230, 5,035,040, and 5,123,273 each disclose a hand held, air-powered tool for applying hog rings for use in conventional applications. These prior art tools each utilize a complex mechanical linkage and jaw arrangement for deforming the hog rings, which arc fed in one-at-a-time from a magazine. Additionally, U.S. Pat. No. 5,483,815, utilizes a rather complex and inefficient series of cams and jaws retained together by a neoprene O-ring. However, hog rings and similar fasteners have not previously been used in conjunction with the construction industry to secure reinforcement members. Conventional hog rings are too small for this purpose and have not heretofore been recognized as a possible solution to the high labor costs associated with concrete construction. Moreover, prior art devices used to apply hog rings and similar fasteners have disadvantages that make the devices expensive and inefficient to manufacture. The disadvantages of each of the aforementioned applicator tools are further exaggerated when used to apply the larger fastener clips associated with concrete construction.
There exists, therefore, a need for a hand held apparatus for tying fasteners for use in concrete construction that efficiently secures reinforced members while retaining the low costs associated with the use of manual power.